Isokinetics and Exercise Science - Volume 14, issue 3

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Isokinetics and Exercise Science (IES) is an international journal devoted to the study of theoretical and applied aspects of human muscle performance. Since isokinetic dynamometry constitutes the major tool in this area, the journal takes a particular interest in exploring the considerable potential of this technology.

Isokinetics and Exercise Science publishes studies associated with the methodology of muscle performance especially with respect to the issues of reproducibility and validity of testing, description of normal and pathological mechanical parameters which are derivable from muscle testing, applications in basic research topics such as motor learning paradigms and electromyography. The journal also publishes studies on applications in clinical settings and technical aspects of the various measurement systems employed in human muscle performance research.

Isokinetics and Exercise Science welcomes submissions in the form of research papers, reviews, case studies and technical reports from professionals in the fields of sports medicine, orthopaedic and neurological rehabilitation and exercise physiology.

Abstract: The aims of the present study were to clarify the differences in muscle oxygen dynamics between eccentric (ECC) and concentric (CON) contractions and to investigate the relationship between muscle oxygen dynamics and the pattern of skeletal muscle recruitment during ECC and CON contractions. Fifteen healthy male subjects (age 21.8 ± 2 yrs) performed isokinetic ECC and CON knee extension and flexion exercise for 1 min at an angular velocity of 180°/s. Changes in muscle…oxygenation (MO) levels in the active muscle were measured using near-infrared spectroscopy (NIRS) whose probe was placed on the rectus femoris. Bipolar surface electrodes recorded the electromyogram (EMG) activity of this muscle. The MO levels during ECC contraction were significantly higher at 10 s and 15 s after the onset of exercise while MO levels during CON contraction were significantly higher 60 s following the onset of exercise. A significant correlation was indicated between MO levels and EMG activity during CON contraction (p<0.05). These results reveal that oxygen supply-consumption balance in ECC and CON contraction are different. Moreover, this suggests that muscle activity in CON contraction increases and the oxygen supply to active muscle may exceed the oxygen consumption in active muscle.
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Abstract: The purpose of the present study was to determine the effects vibration, applied with different frequencies at different joint angles, on maximal isometric muscle contraction. Forty male volunteers were randomly and equally assigned to one of the four different vibration stimulation groups as 6 Hz, 12 Hz, 24 Hz and 48 Hz. Subjects performed three consecutive isometric maximal voluntary contractions (MVC) with and without vibration for six seconds with one-minute interval at 90, 120 and 150…degrees of elbow angles in random order. During MVC with vibration tests vibration was applied to upper arm 10 seconds before the contraction begins and continued throughout the MVC. According to results of 4 × 3 × 2 ANOVA with repeated measures, significant joint angle effect (p<0.001), contraction type effect p<0.001) and significant frequency × contraction type interaction (p<0.001) was found. It can be concluded that vibration stimulation resulted in increased isometric MVC. Results also suggested that stimulating muscles with 6, 12 and 24 Hz of vibration resulted in increased isometric MVC, 48 Hz of vibration on the other hand resulted in decreased isometric MVC. In addition, the length of the contracting muscle did not affect the vibration load that was applied with different frequencies.
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Abstract: Building on a previous meta-analysis, this study focused on the utility of consolidating grip strength data from apparently healthy subjects 20–49 years of age. All data were obtained using a Jamar dynamometer and procedures generally consistent with the recommendations of the American Society of Hand Therapists. The meta-analysis revealed that the seven sources provided homogeneous data (Q=0.21–0.81, p>0.667) for the left and right sides of men and women subjects. Means and confidence intervals are…provided that can be used to interpret the normality of grip strength obtained from men and women 20–49 years of age. By consolidating the data from multiple studies conducted in five countries, a better overall estimate of normal is obtained. Providing reference values for three decades combined simplifies normative comparisons.
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Abstract: The overall aim was to investigate the fatigue pattern and perceived fatigue during repetitive dynamic contractions in young and older men and women. Sixteen older men and women (mean age 73 ± 3 years) and 22 young men and women (mean age 28 ± 6 years) performed 100 repeated maximum concentric isokinetic knee extension contractions at 90°·s^{-1} (1.57 rad·s^{-1} ). Throughout the 100 contractions, peak torque (PT) and surface…electromyography (EMG) signals from the rectus femoris muscle and the vastus lateralis muscle were recorded simultaneously, together with perceived fatigue (CR-10 scale of Borg). The mean frequency of the power spectrum (MNF) and the root mean square of the signal amplitude (RMS) of the EMG were affected by age and with a sex related difference but for PT the difference of the fatigue pattern was most evident between the sexes. In addition, the young men rated the highest fatigue. Based on EMG, PT and ratings of perceived fatigue it was concluded that the old men fatigued most, the old women fatigued least and the young men perceived greatest fatigue.
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Abstract: The assessment of thigh adductors' strength and endurance and electromyographical (EMG) characteristics has received little attention compared to other muscle groups. The aim of this study was to investigate strength, endurance performance and EMG characteristics of m. adductor longus and m. gracilis during concentric thigh adduction in soccer and bandy players. Muscular endurance was evaluated using the torque reduction during 70 repeated maximum concentric adductions at an angular velocity of 60°/s.…The EMG mean frequency (MNF) and the signal amplitude ratio (SAR, index for muscles' ability to relax between contractions) were analysed. Peak torque decreased significantly throughout the test and no significant differences were found between the two groups. In both muscles, MNF decreased significantly throughout the test. There were no significant differences in MNF and in SAR variables between soccer and bandy players. In conclusion, the present findings reveal a number of significant aspects related to strength and electromyography of hip adductors.
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Abstract: Objective: To compare the associations between different physical activity histories and anthropometric measures in isokinetic lifting performance, isometric back extension endurance and psychophysical lifting tests. Background: The relative roles and interaction of these factors related to back function are largely unknown. Methods: The subjects consisted of a population-based sample of 210 working-age males. Paraspinal muscle cross-sectional areas were obtained by magnetic resonance imaging; anthropometric measures, isokinetic and psychophysical…lifting capacity, and isometric back extension endurance tests were performed and current and physical activity histories and occupational loading were enquired by structured interview. Stepwise multiple regression analyses were used to study the associations. Results: Lean body weight, body weight and sum of the paraspinal muscle CSAs at L3-L4 level predicted the highest amount of the variance (R^2 =10–25%) and the different models of anthropometric measures and physical activity 7–33% of the variance in the back function tests. Conclusions: The models of physical activity and anthropometric measures or their combination predicted isokinetic lifting performances weakly and other back function test results even worse. As a single predictive factor, lean body weight showed weak ability to predict isokinetic lifting performances. Collecting current or past data of physical activity parameters does not add anything for predicting back function.
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Abstract: Objective: To examine the influence of the spinal contour changes on the functioning of trunk muscles in children with idiopathic scoliosis. Background: In the early stage of scoliosis progression, changes in the sagittal plane often manifest themselves in curving in the lumbar lordosis and curving out of the thoracal scoliosis. An increase or decrease in the size of anteroposterior spinal curvatures may disturb functioning of the trunk muscles. Method: Thirty five girls (mean age: 14.7 ±…2.3 yr) with idiopathic scoliosis took part in this study. In terms of location, thoracal scoliosis was dominant. Photogrammetry with automatic Moiré fringe analysis system was used to assess the spinal contour. Activity of the spinal flexors and extensors was tested isokinetically at 3 angular velocities: 60, 90 and 120°/s. The measured force-velocity parameters were analysed according to location of the scoliosis (primary thoracal or primary thoraco-lumbar scoliosis), the size of the deformity and posture type: lordotic, kyphotic or equivalent (balanced) (a posture type, where thoracic kyphosis and lumbar lordosis are of similar size – they are balanced). Results and conclusions: A step-by-step discriminant analysis indicated that parameters associated with muscle endurance were the most diversified regardless of the division criterion applied. It was also revealed that functioning of the trunk muscles was related to the spine asymmetry in the frontal plane as well as on the spinal contour in the sagittal plane.
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Abstract: The purpose of the study was to identify the sport-specific range of joint angles for the knee extensors' muscular strength during isometric evaluation. Twenty young female track and field jumpers (J) and 21 volleyball players (V), aged 13–19 years, participated in the study. The values of torque at the initial 200 ms (T_{INIT} ) and of maximum torque (T_{MAX} ) were determined from the torque-time curve at each knee angle. A 2 (Group) ×…9 (Angle) ANOVA was applied to examine the between group differences of T_{INIT} and _{MAX} . Principal component analysis (PCA) followed by varimax rotation was performed to investigate the angle sport-specificity of_{INIT} and T_{MAX} . Track and field jumpers demonstrated higher torque values, however, these values did not yield statistical significance at all knee angles (p> 0.05), either for T_{INIT} or T_{MAX} . PCAs revealed an angle sport-specific loading of _{INIT} and T_{MAX} , which were heavier loaded on the first component at the angles closer to full knee extension and at the angles closer to knee flexion, in the track and field jumpers and the volleyball players, respectively. These findings provide evidence for the knee angles to be included in a more specialized sport-specific isometric evaluation.
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Abstract: Objective: To evaluate bilateral quadriceps and hamstrings strength, at two different ranges of motion (RoM): 30° (SRoM) and 90° (FRoM), using different angular velocities. Background: Recent studies have indicated that short RoM isokinetic testing of knee muscles yielded strength findings that were compatible with those derived from a much larger RoM. However, findings were based on a single adjusted velocity in each of the RoMs. Method: Sixteen healthy male students volunteered to…participate in this study. Two testing sessions, a week apart, were performed. In the first session testing started with a RoM of 90° (FRoM, 0° – full extension) and angular velocities of 60 and 180°/s. Measurements related to concentric (quadriceps and hamstring) and eccentric (quadriceps only) contractions. In the second part of the test, the RoM was adjusted to 30° (SRoM, 30–60° knee flexion) with velocities of 30 and 60°/s, respectively. The order of RoM testing was reversed in the second session. All tests were conducted bilaterally. Results: Both FRoM- and SRoM-based scores have shown good reproducibility based on the Bland Altman plots and low values of standard error of measurement and coefficient of variance of standard deviation. No statistically significant differences were noted between the FRoM and SRoM-based strength scores. The results suggest that range of motion used in isokinetic testing alone or in combination with other factors, namely side tested and isokinetic velocity, does not significantly influences changes in peak torque values for both quadriceps and hamstrings. Conclusion: This study suggests that SRoM isokinetic testing provides an effective alternative to the commonly applied range.
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Abstract: To determine optimal parameters for representing knee flexion and extension strength in athletes and describe reference values for track and field athletics, 248 high-level Spanish athletes of 22 different specialities and a group of 68 sedentary subjects were tested isokinetically at 60 and 300°/s. Absolute and weight normalized strength of the flexors and extensors as well as the hamstrings/quadriceps ratio (H/Q60, H/Q300) were studied. Significant correlations were found among all flexion and extension…and between the H/Q ratios. Comparative analysis revealed significant differences among groups for the strength at 60°/s and largely no differences in the H/Q ratio. It is concluded that for discriminating between groups the peak torque at 60°/s is sufficient. Moreover as the athletic specialty has no effect on the H/Q ratio its use for this particular purpose should be discontinued.
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